The invention relates to an aggregate at the end of a boom in a vehicle-mounted crane and to a method by means of which a tree is felled, delimbed and crosscut.

Previously known is an additional timber grapple aggregate as per the Finnish publication No. 84219, which gets is motive power by the timber grapple motion and by means of which delimbing and crosscuting is performed with the tree still in upright position. The aggregate is made of two scissors- shaped arms fixed together by a joint. At the other end of the aggregate there are fastening means for fastening the aggregate to the grapple arms on the grapple side. In opening and closing the arms, the gap between the delimbing knives can be adjusted. Likewise, reckoned from the joint, the shorter arms have cutting knives, by means of which the tree is cut into lengthes in opening and closing the arms. Delimb¬ ing is carried out in moving the aggregate along the trunk while the knives are delimbing with the tree still in upright position.

The disadvantage of the design according to said publication is the long construction of the aggregate, which is due to the scirrors-shape of the arms. So the crosscutting knives must be arranged on the other side of the scirrors joint with respect to the delimbing knives. The weigth of device becomes great, because the arms must be of heavy-duty type due to their length and great torsional forces. The limited out¬ reach at delimbing and great inaccuracy of crosscuttings is an additioal disadvantage of the method.

These disadvantages are avoided by means of the inventional aggregate mounted at the end of a crane boom and the invent¬ ional delimbing and crosscutting method. The invention is characterized in what is presented in the enclosed patent claims.

The light weight of the delimbing and crosscutting aggregate compared with present harvester aggregates can be considered the most important advantage of this invention. In an aggre¬ gate as per this invention there are neither tree moving rol¬ lers nor hydraulic cylinders to feed driving force, because the aggregate is moved on the tree surface by means of the boom system motions. Since delimbing is carried out in front of the machine and the tree is taken to the machine by pul¬ ling it from the butt in the tree direction, as little as possible damage is caused to the saplings and remaining trees. Smaller trees can be brought even in uprigt position from the stump to the machine with the aggregate and the boom.

In the following the invention is presented in detail with reference to the enclosed drawings, where

•Fig. 1 is an aggregate mounted on a timber crane. Fig. 2 is delimbing with the aggregate.

Figure 1 shows a tractor-mounted timber crane 1 with a mobile boom. An the end of the crane a crosscutting and delimbing aggregate with its frame is fastend. Lowest in the aggregate is a chain saw 9 in a solid housing 8 for cutting the tre into lengthes. In the housing there is a hydraulic motor to operate the saw and a blade 9 turning mechanism for the saw blade cutting motion. Approximately in the middle of the frame there are curved delimbing knives 6 and 7. The delimb¬ ing knives are opened and closed according to the tree dia¬ meter, for instance by means of a hydraulic cylinder, which is not shown in the figure. The delimbing knives are of solid construction and used also to take a good hold around the tree at felling while cutting it off from the butt. By means of the chain saw 9 sturdy housing the tree is also suspended at felling. On the upper side of the delimbing knives there is an immobile delimbing knife 5 to delimb the upper side of the trunk. The aggregate is fastened to the boom end by an articulated mechanism, where the aggregate has no free stage

to move in any direction with respect to the boom but only positively driven by the hydraulic cylinder. This means that controlled tree felling is possible with the aggregate. Any¬ how, the aggregate is usable for controlled felling of small sized trees only.

Further, figure 1 shows gripping jaws 2 and 3 on the crane side of the vehicle. The distance of jaws 2 and 3 and their mutual compression is adjusted by a hydraulic cylinder 4. The butt of felled tree 10 is lifted with the aggregate 10 up between jaws 2 and 3 and locked immobile. Jaws 2 and 3 have small angular points. The jaws can be placed also elsewhere as for instance in the turning upper frame of the crane or even in the lower end of the first crane boom arm. it may be advantgeous for delimbing that the tree butt is locked high¬ er up.

Figure 2 is a felled tree 11 placed, using aggregate 10 as a lift, between jaws 2 nd 3 and locked by cylinder 4, whereby the tree butt is immobile. Delimbing of tree is carried out in this position in moving the aggregate 10 along the trunk so that delimbing knives 5,6 and 7 cutt off the limbs. With this aggregate it is possible to delimb ab. 7 metres from the butt. With longer trees, a wanted lenght of the tree is cut and the butt log taken off from between the jaws. Then the top end log or logs are lifted up bewteen the jaws and delimbed. The delimbing forces are strong and, accordingly, the compression of jaws must be sufficient. The delimbing aggregate must be in right angle with respect to the trunk and it is necessary to adjust its position during delimbing by means of the boom cylinders. In aggregate 10 there can be rollers, leaning against the trunk, to facilitate the delimb¬ ing motion. Likewise, aggregate 10 can be furnished with a device to measure the cutting lengthes of tree, which can be a roller moving along the trunk or a device measuring the mutual distance of cutting blade 9 and jaws 2,3. In princip¬ le, this device can be a known range finder based, for in¬ stance, on radar reflections, acoustic or electromagnetic

wave motions, triangulation etc.

Crosscutting by means of the delimbing aggregate in a working position as shown in figure 2, where the rotating chain saw is entering and returning to the housing 8. By means of de¬ limbing knives 6,7 timber loading or moving is possible as well as pulling of top log and lifting it up between the jaws 2,3.

In addition to the boom arms in the figures, the known teles¬ copic boom construction is also very well adaptable to de¬ limbing, because it allows straight lined motion of the de¬ limbing aggregate.

Though figures 1 and 2 show the fastening method of positive driven aggregate 10 to the boom, known fastening means of a timber crane or harvester can be used with the aggregate. In this known method, the aggregate is suspended from the end of the outmost boom arm, where it can be tilted in all direct¬ ions. Further, the suspended design includes rotation of aggregate in the vertical suspension axle.

In one embodiment of the invention, the tree clamp 2,3 in a working machine is furnished with a rotting device, by means of which the tree can be rotated upon delimbing. Less than 180° is a quite sufficient tree rotation, whereby the ex¬ ternal surface of the tree can certainly be thoroughly de¬ limbed. In this case, delimbing knives are not needed all around the external surface of the tree.

The invention is not restricted to the introduced embodiment but many modifictions are possible within the limits of the inventional concept presented in the patent claims. The de¬ limbing direction can be from tree top to the butt, whereby the butt must not be locked to the crane or the vehicle frame but a support plate in the vehicle or crane frame is suffic¬ ient, against which the butt or the other end of a cut trunk is supported during delimbing.